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Biomedical subjects

J C Shih

Publications and source records attributed to J C Shih.

At least 55 records · Page 3Linked to original sources
PubMed1999

Cerebral cortical blood flow maps are reorganized in MAOB-deficient mice.

Cerebral cortical blood flow (CBF) was measured autoradiographically in conscious mice without the monoamine oxidase B (MAOB) gene (KO, n=11) and the corresponding wild-type animals (WILD, n=11). Subgroups of animals of each genotype received a continuous intravenous infusion over 30 min of phenylethylamine (PEA), an endogenous substrate of MAOB, (8 nmol g-1 min-1 in normal saline at a volume rate of 0.11 microl g-1 min-1) or saline at the same volume rate. Maps of relative CBF distribution showed predominance of midline motor and sensory area CBF in KO mice over WILD mice that received saline. PEA enhanced CBF in lateral frontal and piriform cortex in both KO and WILD mice. These changes may reflect a differential activation due to chronic and acute PEA elevations on motor and olfactory function, as well as on the anxiogenic effects of this amine. In addition to its effects on regional CBF distribution, PEA decreased CBF globally in KO mice (range -31% to -41% decrease from control levels) with a lesser effect in WILD mice. It is concluded that MAOB may normally regulate CBF distribution and its response to blood PEA.

Animals↗
PubMed1999

Lack of protection from ischemic injury of monoamine oxidase B-deficient mice following middle cerebral artery occlusion.

Adult male wild-type mice received intraperitoneal (i.p.) administration of saline (n = 9) or 10 mg/kg L-deprenyl (n = 9) three times a week for 3 weeks. Mice with targeted inactivation of the monoamine oxidase B (MAO-B) gene received i.p. administration of saline (n = 8). Animals underwent ligation of the left common and external carotid arteries, followed by cauterization of the ipsilateral middle cerebral artery. Twenty-four hours post-surgery, all groups showed right torsion of the torso but no evidence of limb weakness, lateral instability, or circling. Ischemic changes were assessed from digitized video-images of serial sections of the brain stained with Hematoxylin/Eosin. No significant group differences were detected in infarct volume (14-18% of ipsilateral cortex) or in the extent of brain edema (4-7% increase in ipsilateral hemispheric swelling with respect to contralateral side). Our results suggest that absence of the MAO-B gene or inhibition of the enzyme with L-deprenyl are not protective or detrimental in an animal model of acute cortical infarction.

Animals↗
PubMed1999

Prenatal diagnosis of a fetus with distal 10q trisomy.

Distal 10q trisomy is a well-defined but rare syndrome. Most cases are diagnosed in infancy or in childhood and rarely include prenatal findings. We present a case of fetal distal 10q trisomy with abnormal prenatal sonographic findings. A 19-year-old primigravida was referred for genetic counselling at 18 gestational weeks because her husband had a familial history of congenital anomalies. Genetic amniocentesis was thus performed and showed fetal distal 10q trisomy (10q24.1-->qter), 46,XX,der(22)t(10;22)(q24.1;p11.2)pat, resulting from paternal t(10;22) reciprocal translocation. Level II ultrasonograms further demonstrated bilateral hydronephrosis, ventricular septal defect and facial dysmorphism ascertained by three-dimensional ultrasound. The pregnancy was terminated at 22 gestational weeks. Post-mortem autopsy confirmed the sonographic findings. We suggest that abnormal prenatal sonographic findings such as cardio-vascular, renal and facial malformations should alert cytogeneticists to search for subtle chromosomal abnormalities.

Adult↗
PubMed1999

Lack of protection of monoamine oxidase B-deficient mice from age-related spatial learning deficits in the Morris water maze.

Monoamine oxidase B (MAO-B) increases in brain in response to aging and neurodegeneration. Whether such increases represent a risk factor to further neuronal damage or simply represent epiphenomena remains unclear. L-deprenyl, an inhibitor of MAO-B, has been shown to improve learning in aged rodents. However, recent data suggests this may occur through mechanisms independent of its enzymatic inhibition. This study investigates visualspatial learning of MAO-B deficient mice and examines what effects absence of MAO-B has on age-related cognitive decline. Learning was tested in the Morris Water Maze in male transgenic MAO-B knockout mice (KO) ages 2 months (n = 9), 7 months (n = 7), and 17 months (n = 8). Performance was compared to that of wild type (WT) littermates. Animals were given four 60 second trials per day with the submerged platform in the "North" position. Animals received 7 days of learning in which they were introduced into the pool facing the wall, alternating between the "East" and "West" positions. A single probe trial followed on day 8, followed by continuation of the original learning paradigm on days 9 and 10. Subsequently, the platform position was changed to the diagonally opposite quadrant and learning continued on days 11-13, followed by a cue phase in which the platform was made visible. Total distance traveled and latency to the platform was increased in 7- and 17- month old mice, most significantly at the beginning of the acquisition phase. This effect reappeared again in 17- month old mice during the reversal phase. No predominant genotypic differences in latency or distance were observed during any phase of the experiment. Our results show that presence or absence of MAO-B does not appear to alter performance in the Morris water maze. Furthermore, presence or absence of MAO-B does not provide protection from the age-dependent deficits in spatial learning.

Aging↗
PubMed1999

3-D power Doppler cerebral angiography in neonates and young infants: comparison with 2-D power Doppler angiography.

The aims of this study were to evaluate the ability of 3-dimensional (3-D) power Doppler angiography (3DPDA) to depict the intracranial vasculature in infants, to compare with 2-D power Doppler ultrasonography (2DPDU), and to explore the potential clinical applications of this procedure in young infants with brain disorders. We performed 3DPDA in 27 infants. 2DPDU were completed in both sagittal and coronal directions in 12 of these patients. In the other 15, only right sagittal plane images were available for comparison. Using a grading system and with only vessels with more than half of the length demonstrated included for comparison, we compared the Doppler signals of major vessels. 3DPDA could have good visualization in more than 60% of the internal carotid artery, ophthalmic artery, pericallosal artery, callosomarginal artery, internal cerebral vein, vein of Galen, and straight sinus in the sagittal plane. 3DPDA also could have good demonstration in about 50% of basilar artery in coronal plane, and posterior communicating artery, posterior cerebral artery, and lenticulostriate artery in sagittal plane. 3DPDA was better than 2DPDU in demonstrating all the major intracranial vessels in different planes, except the anterior communicating artery. In the anterior communicating artery, neither can demonstrate more than 30%.

Brain Diseases↗
PubMed1999

Schizophrenia, monoamine oxidase activity, and cigarette smoking.

Reduced monoamine oxidase activity has been proposed as a marker for vulnerability to schizophrenia. Reduced monamine oxidase activity has also been shown to occur in cigarette smokers. This study compared monamine oxidase activity level in a matched group of patients with schizophrenia who smoked with a group who did not. Lower levels of monoamine oxidase activity were found in the smokers and this is the likely explanation for the low levels hypothesized as a marker for schizophrenia.

Adult↗
PubMed1999

Arteriovenous malformation of mesosalpinx associated with a 'vanishing' ectopic pregnancy: diagnosis with three-dimensional color power angiography.

We describe two cases of pelvic arteriovenous malformation diagnosed with the aid of three-dimensional color power angiography. In both cases, beta-human chorionic gonadotropin (beta-hCG) increased to significant levels (8413 and 1560 mIU/ml, respectively); however, neither an intrauterine nor an adnexal gestational sac could be found. In each case, we observed an adnexal mass with several tortuous areas exhibiting abundant turbulent flow. The diagnosis of arteriovenous malformation was made and further assessment by three-dimensional color power angiography and magnetic resonance imaging (MRI) was carried out. The complex vascular anatomy of arteriovenous malformation, including its feeding vessels and drainage, was clearly depicted by three-dimensional color power angiography and correlated well with magnetic resonance angiography. Levels of beta-hCG decreased in subsequent tests, and eventually became negative 2-3 months later without and intervention. We believe that an involutional ectopic pregnancy induced the rapid growth of the arteriovenous malformations within the mesosalpinx. Three-dimensional color power angiography can be performed quickly and easily, using existing ultrasound equipment. It improves our understanding of complicated vasculature, and thus is a useful adjunct to two-dimensional and color Doppler ultrasound in the diagnosis of arteriovenous malformation.

Adult↗
PubMed1999

Cervical pregnancy: assessment with three-dimensional power Doppler imaging and successful management with selective uterine artery embolization.

Cervical pregnancy is frequently associated with extensive hemorrhage which, in severe cases, may be stopped only by hysterectomy. We report a case of an anembryonic cervical pregnancy diagnosed at 10 weeks, and associated with a large arteriovenous malformation. The patient was conservatively managed with simple selective uterine artery embolization. After embolization, her vaginal bleeding ceased and the level of serum beta-human chorionic gonadotropin decreased rapidly. No additional treatment was given. The patient's postoperative course was uneventful and the cervical mass had disappeared at the follow-up 4 months later. To the best of our knowledge, this is the first report of conservative management of cervical pregnancy simply by uterine artery embolization. The role of three-dimensional power Doppler ultrasonography in the assessment of cervical pregnancy and in monitoring the therapeutic response is discussed.

Adult↗
PubMed1999

Doppler waveform analysis of the intertwin blood flow in acardiac pregnancy: implications for pathogenesis.

OBJECTIVE: To investigate interfetal hemodynamics in acardiac twins and the implications for pathogenesis. DESIGN: A retrospective study. SUBJECTS: All acardiac twins involved in this study were identified by B-mode ultrasound at a teaching hospital in Taiwan. METHODS: Color Doppler imaging and, in one case, color power angiography were used to assess umbilical blood flow between acardiac twins and their normal co-twins. Placental anastomoses were examined by pathologists after delivery. RESULTS: In total five sets of acardiac twins and their normal co-twins were enrolled. Autonomous cardiac activity in the form of a contractile pocket was detected in two cases. Analysis of the pattern of the Doppler waveforms in each case enabled us to classify the type of hemodynamics into one of three categories: 'collision-summation', typified by a pattern of cyclic alternations of bidirectional flow; 'twin-pulse', which described the simultaneous recordings of two opposite constant flows with different pulsating rates; and the 'pump in' pattern, which indicated pulsatile flow in the reversed direction towards the acardiac mass. In two cases we detected, we believe for the first time, an artery-to-vein placental anastomosis between the acardiac twin and its co-twin. The nature of the vascular connections were confirmed on pathological follow-up. CONCLUSIONS: Our observations suggest that acardiac twins may be not only the result of but also the cause of placental vascular anastomoses, which may involve either artery-to-artery or artery-to-vein anastomoses.

Angiography↗
PubMed1999

Striatal dopamine metabolism in monoamine oxidase B-deficient mice: a brain dialysis study.

We have studied striatal dopamine (DA) metabolism in monoamine oxidase (MAO) B-deficient mice using brain microdialysis. Baseline DA levels were similar in wild-type and knock-out (KO) mice. Administration of a selective MAO A inhibitor, clorgyline (2 mg/kg), increased DA levels and decreased levels of its metabolites in all mice, but a selective MAO B inhibitor, l-deprenyl (1 mg/ kg), had no effect. Administration of 10 and 50 mg/kg L-DOPA, the precursor of DA, increased the levels of DA similarly in wild-type and KO mice. The highest dose of L-DOPA (100 mg/kg) produced a larger increase in DA in KO than wild-type mice. This difference was abolished by pretreating wild-type mice with l-deprenyl. These results suggest that in mice, DA is only metabolized by MAO A under basal conditions and by both MAO A and B at high concentrations. This is in contrast to the rat, where DA is always metabolized by MAO A regardless of concentration.

Animals↗
PubMed1999

Monoamine oxidase: from genes to behavior.

Cloning of MAO (monoamine oxidase) A and B has demonstrated unequivocally that these enzymes are made up of different polypeptides, and our understanding of MAO structure, regulation, and function has been significantly advanced by studies using their cDNA. MAO A and B genes are located on the X-chromosome (Xp11.23) and comprise 15 exons with identical intron-exon organization, which suggests that they are derived from the same ancestral gene. MAO A and B knock-out mice exhibit distinct differences in neurotransmitter metabolism and behavior. MAO A knock-out mice have elevated brain levels of serotonin, norephinephrine, and dopamine and manifest aggressive behavior similar to human males with a deletion of MAO A. In contrast, MAO B knock-out mice do not exhibit aggression and only levels of phenylethylamine are increased. Mice lacking MAO B are resistant to the Parkinsongenic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine. Both MAO A and B knock-out mice show increased reactivity to stress. These knock-out mice are valuable models for investigating the role of monoamines in psychoses and neurodegenerative and stress-related disorders.

Alcoholism↗
PubMed1999

MAO-A and -B gene knock-out mice exhibit distinctly different behavior.

MAO-A and -B are key isoenzymes that degrade biogenic and dietary amines. MAO-A preferentially oxidizes 5-HT and NE, whereas MAO-B preferentially oxidizes PEA. However, the substrate and inhibitor selectivity overlap depending on the concentration of the enzyme and substrate. A line of transgenic mice has been generated in which the gene that encodes MAO-A is disrupted. MAO-A KO mice have elevated brain levels of 5-HT, NE and DA and manifest aggressive behavior similar to men with a deletion of MAO-A. We have also generated mice deficient in MAO-B by homologous recombination. Interestingly, MAO-B KO mice do not exhibit aggression and only levels of PEA are increased. MAO-B-deficient mice are resistant to the Parkinsongenic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Thus, studies of MAO-A and -B KO mice have clearly shown that MAO-A and -B have distinct functions in neurotransmitter metabolism and behavior. MAO KO mice are valuable models for investigating the role of monoamines in aggression and neurodegenerative and stress-related disorders.

Aggression↗
PubMed1998

Transcription factor binding to the core promoter of the human monoamine oxidase B gene in the cerebral cortex and in blood cells.

Many studies show that monoamine oxidase B in blood cells is a biological marker for personality characteristics such as sensation seeking. The mechanism underlying this association is so far not explored. In the present study we have performed electrophoretic mobility-shift assays to investigate the pattern of protein binding to a 150 bp fragment of the proximal 5'-flanking region of the human monoamine oxidase B gene. We compared the pattern using nuclear extracts from human brain and lymphocytes. Interestingly, a correlation was observed between monoamine oxidase B enzyme activity in blood cells (platelets) and the binding pattern of two uncharacterized transcription factors. These data are well in line with the long-standing notion that interindividual differences in platelet monoamine oxidase may represent differences in expression of the enzyme rather than genotypic variation.

Blood Platelets↗
PubMed1998

Prenatal diagnosis of monosomy 10q25 associated with single umbilical artery and sex reversal: report of a case.

The association of rare chromosomal rearrangements involving a specific 10q breakpoint with a single umbilical artery (SUA) and sex reversal has never been reported. This report describes the case of a fetus with prenatal ultrasound features of severe intrauterine growth retardation (IUGR), congenital heart disease, and SUA. Fetal blood study revealed de novo deletion of 10q25 and a 46,XY karyotype, while ultrasound demonstrated female genitalia. Based on these findings, sex reversal was diagnosed. Polymerase chain reaction (PCR) amplification revealed the presence of the sex-determining region of the Y (SRY) gene. The pregnancy was terminated at 36 weeks and the newborn weighed 1908 g with marked facial dysmorphism and abnormal genitalia. Because the parents refused autopsy for this case, histopathological examination of gonads was not performed. Breakpoint of the long arm of chromosome 10 may be responsible for sex reversal in the present case and it could thus confirm the concept of autosomal sex reversal proposed in previous reports.

Abortion, Induced↗